It has long been the practice in the construction of wheels for trucks and other heavy duty highway or off-highway vehicular equipment, including military vehicles, to provide a "multi-piece" type or a "take-apart" type wheel assembly, each type utilizing a rim of the split-type in order to facilitate the mounting or demounting of heavy duty tubeless pneumatic tires thereon. In such multi-piece and take-apart wheels, it has also been conventional to employ a sealing member, such as an O-ring or other sealing ring having especially contoured cross-sectional configurations, which is interposed between the removable flange ring and the other disc and rim parts of the wheel to seal the tire and rim to maintain the necessary air tightness between them.
Take-apart wheels are an integral part of several systems designed to provide enhanced mobility for army pneumatic tire vehicles, such as the High Mobility Multi-Purpose Wheel Vehicle (HMMWV). Such wheels provide the ability to insert devices into the tire cavity for run-flat capability or bead lock to prevent tire bead unseating when operated at the low inflation pressure as necessary for soft soil floatation.
The difference between a "Take-apart" type wheel and the more common multi-piece, lock ring and gutter style of wheel is that the former is a bolt-together type of wheel. This allows repeated assembly/disassembly with common hand tools. It also provides a means of axially compressing the tire beads against a bead locking device which simulates inflation pressure sufficient to prevent bead unseating under low or no inflation pressure conditions.
In order to be able to insert either run-flat or bead lock devices into the tire cavity, the tire must be of the tubeless type. This requires the two rim halves of the take-apart wheel to be sealed to prevent air loss. Several seal types have been utilized experimentally, but the easiest and least expensive has been found to be the common O-ring type of seal. To meet the demand for army mobility requirements for varying tire inflation pressures, depending upon terrain conditions, vehicle manufacturers have developed Central Tire Inflation Systems (CTIS) which allow the crew to change the inflation pressure in a few minutes without leaving the vehicle cab. This is accomplished by an on-board compression valving and piping system with an on-dash control switch.
For further details regarding various facets of take-apart wheels for high mobility military applications, reference may be made to SAE Technical Paper No. 880694 entitled "Take-Apart Wheels for High Mobility Military Applications" by J. Bruce Weeks of Motor Wheel Corporation presented at the SAE International Congress and Exposition, Detroit, Mich. on Feb. 29-Mar. 4, 1988.
Examples of improvements in such prior art take-apart wheels with sealing members may be found in the following prior art U.S. Pat. Nos. assigned of record to the assignee herein, namely, Strader 4,327,791; Strader 4,481,997; Payne et al 4,823,854; and Weeks et al 4,836,261. These patents disclose take-apart military vehicle wheels employing O-ring sealing and adapted to be equipped with a safety insert device disposed internally of a tubeless tire mounted on the rim for supporting the tire tread in a deflated condition to thereby provide a so-called "run-flat" wheel construction.
In safety tire and wheel assemblies which include inserts of the described type, the insert conventionally comprises a base portion disposed adjacent the wheel rim and a second portion projecting radially from the rim into the tire cavity or chamber. Upon loss of air pressure in the chamber, the tire tread collapses against the second portion of the insert such that the insert supports the tire tread with respect to the rim for continued operation of the vehicle. Alternatively, the insert may comprise merely a base portion adapted to operate as a so-called "bead-lock" to prevent slippage of the tire beads relative to the rim bead seats and tire bead retaining flanges under high torque and/or low inflation pressure conditions, and/or to prevent loss of the tire from the rim under such conditions.
The aforementioned Strader '997 patent also discloses and claims an important safety feature useful in a multi-piece wheel rim assemblies, whether considered alone or in combination with safety inserts of the above-described type, which overcomes a significant safety hazard if it is attempted to inflate a tire mounted thereon when the various wheel assembly components are improperly positioned or seated, or to disassemble the rim when the tire mounted thereon has not been completely deflated. In the Strader '997 patent wheel construction, the disc and inboard rim part are made as one piece, and the O-ring is captured between a shoulder, at the junction of the disc with the inboard rim part, and an up-turned flange at the inner edge of the outboard rim part. Safety vent means, such as a groove or aperture in the disc-inboard rim piece, is located on the outboard side of the seal when in assembled position. Such safety vent means is operative to prevent inflation of a tire mounted on a wheel assembly when the wheel assembly components are improperly positioned and/or to automatically vent the tire cavity to atmosphere prior to disconnection of the outboard rim part should disassembly be attempted when the tire mounted thereon is still fully or partially inflated.
In the aforementioned Weeks et al '261 patent such safety air bleed means comprises a shoulder radius on the disc between the central wheel mounting portion of the disc and the outer surface of the outer marginal flange of the disc. The O-ring seal is displaceable by a tire interior air pressure axially along the disc outer surface onto the disc shoulder radius to thereby lose sealing engagement with the sealing surfaces to allow complete tire deflation as the wheel assembly nuts are loosened but while still engaged with their associated threaded studs.
One safety problem remains with such wheels when made to heavy duty military specifications which has thus far prevented their use in non-military applications, namely, the relatively large diameter rim hole provided to mount the military-specified inflation valve hardware. This valve hole is large enough to permit insertion therethrough of the built-in inflation valve of an inner tube, enabling the same to be improperly utilized as a "field fix" to salvage or prolong the use of a damaged tubeless tire mounted on the wheel. Although this unsafe practice is not condoned in military usage, it must be prevented if such take-apart wheels are to be made and marketed for commercial usage in order to prevent the safety air bleed feature of take-apart wheels from being improperly defeated in the field by the aforementioned inner tube "fix".
More particularly, it is not uncommon in commercial applications that, when a tubeless tire is damaged, such as by a side wall cut, the vehicle operator or service mechanic will make a "field fix" by installing an inner tube in the otherwise tubeless pneumatic tire so that the tire can continue in service even though damaged. However, when this fix is employed with a take-apart wheel, a dangerous condition is thereby created because the inner tube inside the tire defeats the O-ring air escape safety feature described previously hereinabove. Since automatic deflation of the tubeless tire upon initial partial disassembly of the wheel is no longer assured, the outboard demountable disc and/or rim part can be forceably blown off the remaining wheel and tire parts during wheel disassembly by the bead expansion force of the inflated inner tube, thereby creating a potential hazard which may cause injury to person and property. In other words, if an inner tube is installed in a tubeless tire on such a wheel, there is no safety air escape to deflate an inflated inner tube and hence, if not properly fully deflated, its expansion force can cause the wheel to fly apart during disassembly even though the interior tire cavity may be safety vented to atmosphere.
The aforementioned "inner tube fix" is not considered a problem in military applications because it is not military practice to repair damaged tubeless tires by inserting inner tubes in the same, but rather to proceed with 100% replacement of damaged tubeless tires with new, undamaged tubeless tires. Moreover, in military applications in which the take apart wheel is equipped with a run-flat insert 90 or the like, the tire/wheel assembly can be run deflated until the tire is replaced.
Thus, although the aforementioned safety wheel and run-flat wheel constructions have been successfully built and tested for use on military vehicles, certain problems nevertheless remain, such as the aforementioned lack of safe convertibility of a military specified design to non-military heavy duty truck use for the commercial on-highway and off-highway markets, as well as the continuing need to improve the rim-to-brake clearance for a given wheel size, the desirability of employing a standardized disc for various rim parts having thicknesses differing from the disc, and vice versa, while retaining the ability to accommodate a variety of wheel offsets from a standard set of component parts. Moreover, it is desirable from the manufacturing cost standpoint that the above parameters be satisfied in a wheel construction which can be made on existing conventional stamping equipment with respect to the disc, and wherein the rim parts can be made on conventional roll forming or die stamping equipment so that spin forming equipment operations need not be utilized in the manufacture of the wheel, and so that the two-part wheel subassembly can be made on conventional and existing rim-disc press fit and welding equipment.
Another type of take-apart wheel construction employs a one-piece wheel disc integral with an outboard tire bead seat portion and outboard tire bead retaining flange, which is removably secured by bolts to an inboard rim part comprising a inboard tire bead retaining flange, rim bottom portion, usually of cylindrical configuration, and a radially in-turned mounting flange. Examples of this type of take-apart wheel construction may be found in the following U.S. Pat. Nos.:
______________________________________ Mitchell 3,865,170 Mitchell 3,885,615 Sano 4,106,543 Osada et al 4,216,810 Okada 4,228,840 Osada et al 4,372,365 ______________________________________
However, none of such prior art proposals would appear to provide a safety tire and take-apart wheel construction which would fulfill all of the stated objects of the present invention nor provide the features and advantages of the same.
Accordingly an object of the present invention is to provide an improved take-apart wheel rim assembly utilizing a tubeless pneumatic tire, and having a safety vent feature, which overcomes the aforementioned problems present in such wheel constructions, optimizes the aforementioned desirable product design and manufacturing parameters and which is safely usable in either military or commercial applications.